The long term goal of this research is to elucidate the relationship between the molecular mechanism of anesthesia and the perturbation by general anesthetics of the physical properties of lipid membranes. The specific objectives are to determine whether the incorporation of general anesthetics into artificial lipid membranes (liposomes) affects the rate or extent of bilayer hydration of nonphosphatidylcholine lipids, whether such an effect on hydration is correlated with anesthetic potency, whether such an effect is reversible upon application of hydrostatic pressure, and whether such an effect inhibits the fusion of phospholipid vesicles. Scanning calorimetry, infrared spectroscopy, and fluorescence spectroscopy will be employed to make these determinations. Scanning calorimetry provides a probe for determining the effect of anesthetics on phase transitions, the formation of non-bilayer phases, and, indirectly, membrane hydration. Infrared spectroscopy provides a direct probe for the extent of membrane hydration, and an assessment of the structural perturbation of the lipid bilayer by general anesthetics. In addition, it provides a means for localizing anesthetics within the bilayer. Fluorometry is used to assess the perturbation by general ansesthetics of calcium-induced membrane fusion, using energy transfer between reporter molecules in the lipid bilayer. Measurements of anesthetic effects on membrane phase transitions, hydration, and fusion, will be carried out under both low and high pressure. Finding such effects would make plausible the theory that general anesthetics work by inhibiting the dehydration of presynaptic vesicles within the nerve terminal, fusion of these vesicles with the presynaptic membrane, and neurotransmitter release.